Conventionally, a board-mount electrical connector having plural terminals, and a housing which holds these terminals is described, for example, in Japanese Patent No. 3538747. Here, in the electrical connector shown in Japanese Patent No. 3538747, each terminal has at one end a male contact section which extends substantially parallel with the circuit board in the housing. The male contact section is inserted into a female contact of a mating connector, and has at the other end a connecting section which extends in a direction substantially perpendicular to the circuit board outside the housing which is soldered to the circuit board. A portion between the contact section and the connecting section is formed to bend behind a rear wall of the housing to reach the connecting section.
For each terminal, tin-plating is applied to the entire terminal from the contact section to the connecting section, and a relatively thick tin-plated layer is formed on the connecting section which is soldered to the circuit board for the following reason. For the terminal of the electrical connector, a copper alloy including zinc is used as a base material, and when tin-plating is applied to such a base material, in time, an alloying phenomenon of tin and zinc which is precipitated inside the tin-plated layer from the base material advances in the tin-plated layer from the base material side to the surface. Here, if the storage time of the electrical connector is too long and the alloying phenomenon reaches the surface of the tin-plated layer, the alloy of tin and zinc appears on the surface. This alloy prevents affinity of the connecting section and solder at the time of soldering, and reduces solderability of the connecting section. Therefore, a relatively thick tin-plated layer is formed on the connecting section, and the allowable time before the alloying phenomenon reaches the surface of the tin-plated layer is made longer, so that favorable solderability of the connecting section can be maintained for a long term.
However, in the terminal of the electrical connector, internal stress remains at a bent portion between the contact section and the connecting section, and there is a possibility that an electrically conductive needle crystal called “a whisker” that grows with time occurs on the tin-plated surface of the terminal due to such internal stress. If such a whisker occurs on the terminal of the electrical connector, there arises the problem that, for example, the whisker electrically short-circuits the adjacent terminals and the like.